Molecular bases of an alternative dual-enzyme system for light color acclimation of marine Synechococcus cyanobacteria
Molecular bases of an alternative dual-enzyme system for light color acclimation of marine Synechococcus cyanobacteria
复制标题
DOI：
10.1073/pnas.2019715118
复制
发表时间：
2021-03-02
影响因子：
11.1
通讯作者：
Partensky, Frederic
中科院分区：
文献类型：
--
作者：
Grebert, Theophile;Nguyen, Adam A.;Partensky, Frederic
海洋聚藻蓝藻的普遍存在部分归功于其光收集复合物的广泛色素多样性。在开阔的海水中，细胞主要具有复杂的触角，由藻蓝蛋白和两种类型的藻蓝蛋白（PEI和PEII）组成。一些菌株专门用于收集绿光或蓝光，而其他菌株可以动态修改其光吸收光谱以匹配主要环境颜色。这一过程被称为IV型色驯化（CA4），与两种构型（CA4- a和CA4- b）中出现的小基因组岛有关。虽然CA4-A过程已被部分表征，但CA4-I3过程仍然是一个谜。本文研究了粘球菌菌株A15-62中藻胆素裂解酶E/F家族的两个成员MpeW和MpeQ的功能，并证明了它们在CA4-B中的关键作用。MpeW编码于CA4-6岛，在绿光下上调，在绿光下将绿光吸收的发色团藻红蛋白附着在PEII α -亚基的半胱氨酸-83上，而MpeQ在蓝光下与藻红蛋白结合并在同一位点异构为吸收蓝光的藻红蛋白，逆转了CA4-A菌株RS9916中MpeZ和MpeY的关系。因此，我们的数据揭示了两种类型的色适应物之间的关键分子差异，它们都非常丰富，但在海洋中占据着不同的互补生态位。它们还支持一种进化情景，即获得CA4-B岛允许前蓝光专家成为色适应者，而前绿光专家将通过获得CA4-A岛获得这种能力。
Marine Synechococcus cyanobacteria owe their ubiquity in part to the wide pigment diversity of their light-harvesting complexes. In open ocean waters, cells predominantly possess sophisticated antennae with rods composed of phycocyanin and two types of phycoerythrins (PEI and PEII). Some strains are specialized for harvesting either green or blue light, while others can dynamically modify their light absorption spectrum to match the dominant ambient color. This process, called type IV chromatic acclimation (CA4), has been linked to the presence of a small genomic island occurring in two configurations (CA4-A and CA4-B). While the CA4-A process has been partially characterized, the CA4-I3 process has remained an enigma. Here we characterize the function of two members of the phycobilin lyase E/F clan, MpeW and MpeQ, in Synechococcus sp. strain A15-62 and demonstrate their critical role in CA4-B. While MpeW, encoded in the CA4-6 island and up-regulated in green light, attaches the green light-absorbing chromophore phycoerythrobilin to cysteine-83 of the PEII alpha-subunit in green light, MpeQ binds phycoerythrobilin and isomerizes it into the blue light-absorbing phycourobilin at the same site in blue light, reversing the relationship of MpeZ and MpeY in the CA4-A strain RS9916. Our data thus reveal key molecular differences between the two types of chromatic acclimaters, both highly abundant but occupying distinct complementary ecological niches in the ocean. They also support an evolutionary scenario whereby CA4-B island acquisition allowed former blue light specialists to become chromatic acclimaters, while former green light specialists would have acquired this capacity by gaining a CA4-A island.